Coordination for ocaml related backports.

Problematic: the backports available at http://www.backports.org/ need to be coordinated. As for testing, we need to rebuild every module with the latest ocaml package.

This comes for all newly introduced packages backported from testing that were not in the latest stable, as well as stable packages, when the ocaml version in backports.org in not the same as in stable.

Build dependencies can be very tricky. You have to keep in mind that they are resolved while trying to use as less as possible the packages from backports.org. From instance, if ocaml-findlib pulls ocaml-nox-3.09.x in current stable, and the source package also have a versioned build dependency on a more recent ocaml-nox, then the resolution will fail.

The safe solution for now is to version as much as possible the build dependencies when backporting. This also goes for ocaml related binary dependencies. Indeed, if your package binary-depends on an unversioned package, then the resolver will pull the one from stable and then fail for the very same reason...

Also, it's important to check that every build-dep has been built on all available archs before uploading a module depending on it. Indeed, there does not seem to have new build attempts after a failed build on backports.org